Positive resist compositions and patterning process

ABSTRACT

A positive resist composition comprises (A) a resin component which becomes soluble in an alkaline developer under the action of an acid and (B) an acid generator. The resin (A) is a polymer comprising specific recurring units. When processed by ArF lithography, the composition is improved in resolution and forms a pattern with a minimal line edge roughness.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2006-321870 filed in Japan on Nov. 29, 2006,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a positive resist composition for themicropatterning technology which forms a pattern with an improvedresolution, pattern density dependency, mask fidelity, andrectangularity while suppressing film slimming, and a patterning processusing the same.

BACKGROUND ART

In the recent drive for higher integration and operating speeds in LSIdevices, it is desired to miniaturize the pattern rule. Great effortshave been devoted for the development of the micropatterning technologyusing deep-ultraviolet (deep-UV) or vacuum-ultraviolet (VUV)lithography. The photolithography using KrF excimer laser (wavelength248 nm) as the light source has already established the main role in thecommercial manufacture of semiconductor devices. The lithography usingArF excimer laser (wavelength 193 nm) is under investigation to enablefurther miniaturization and has reached the stage of prototypemanufacture experiments. However, the ArF excimer laser lithography hasnot matured so that many problems must be overcome before the technologycan be applied to an industrial scale of semiconductor manufacture.

The requisite properties for the resist materials to comply with the ArFexcimer laser lithography include transparency at wavelength 193 nm anddry etch resistance. Resist materials comprising as a base resinpoly(meth)acrylic acid derivatives having bulky acid-labile protectivegroups as typified by 2-ethyl-2-adamantyl and 2-methyl-2-adamantylgroups were proposed as having both the properties (JP-A 9-73173 andJP-A 9-90637). Since then, a variety of materials have been proposed.Most of them commonly use resins having a highly transparent backboneand a carboxylic acid moiety protected with a bulky tertiary alkylgroup.

While these resist materials suffer from several problems, thefluctuation of pattern line width, known as “line edge roughness” (LER),becomes serious in forming finer size patterns. Particularly in theprocessing of gate electrode zones in the LSI circuit manufacturingprocess, the LER can cause a fatal defect. It is believed that the LERis affected by various factors. The main factor is the poor affinity ofa base resin to a developer, that is, low solubility of a base resin ina developer. Since carboxylic acid protective groups commonly used inthe art are bulky tertiary alkyl groups and thus highly hydrophobic,most of them are less soluble. Where a high resolution is required as inthe formation of microscopic channels, a noticeable LER can lead to anuneven size, resulting in transistors with degraded electricalproperties. One of known approaches for reducing LER is by increasingthe amount of photoacid generator added, as described in Journal ofPhotopolymer Science and Technology, vol. 19, No. 3, 2006, 313-318.Another approach is by rendering more hydrophilic the basic additive forcapturing the generated acid, as described in Journal of PhotopolymerScience and Technology, vol. 19, No. 3, 2006, 327-334. These approaches,however, exert a less than satisfactory effect.

One of the factors that degrade line edge roughness (LER) is amicro-swelling phenomenon that a resist pattern is swollen as adeveloper penetrates into the resist pattern. One known approach foranti-swelling is the use of a resin containing a fluoroalcohol partialstructure, as described in Journal of Photopolymer Science andTechnology, vol. 18, No. 3, 2005, 381-387. The introduction offluoroalcohol restrains the resin from swelling, but entails thenegative effect of facilitating acid diffusion during heat treatmentfollowing exposure (i.e., post-exposure baking, PEB). This invitesdegradation of resolution, failing to gain a satisfactory process window(focal depth, exposure margin, etc.).

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a positive resist compositionwhich meets both a high resolution and a pattern rectangularity whenprocessed by the photolithography using high-energy radiation such asArF excimer laser light as a light source, and a patterning processusing the same.

The inventor has found that a positive resist composition comprising apolymer comprising specific recurring units as a base resin possesses anexcellent resolution performance and reduces LER when processed by thephotolithography. The composition is thus quite effective for precisemicropatterning.

In one aspect, the invention provides a positive resist compositioncomprising (A) a resin component which becomes soluble in an alkalinedeveloper under the action of an acid and (B) a compound capable ofgenerating an acid in response to actinic light or radiation. The resincomponent (A) is a polymer comprising recurring units having the generalformula (1):

wherein R¹ is each independently hydrogen, methyl or trifluoromethyl, R²is hydrogen or CO₂R⁴, R³ is a fluorinated substituent group of 1 to 15carbon atoms, R⁴ is a straight, branched or cyclic monovalenthydrocarbon group of 1 to 20 carbon atoms which may contain aheteroatom, m is 1 or 2, n is 1 or 2, a, b, c, and d indicative ofratios of the corresponding recurring units each are a number from morethan 0 to less than 1, and a+b+c+d=1.

In another aspect, the invention provides a process for forming apattern, comprising the steps of applying the resist composition definedabove onto a substrate to form a resist coating; heat treating thecoating and exposing to high-energy radiation or electron beam through aphotomask; and heat treating the exposed coating and developing with adeveloper.

In one preferred embodiment, the exposing step is effected by theimmersion lithography wherein a liquid having a refractive index of atleast 1 intervenes between the resist coating and a projection lens.

In another preferred embodiment, the process further comprises the stepof applying a protective coating on the resist coating, and the exposingstep is effected by the immersion lithography wherein a liquid having arefractive index of at least 1 intervenes between the protective coatingand a projection lens.

BENEFITS OF THE INVENTION

When processed by the micropatterning process, especially ArFlithography, the positive resist composition of the invention exhibits asignificantly high resolution and forms a pattern with a minimized LER.The composition is thus quite effective for precise micropatterning.

PREFERRED EMBODIMENTS OF THE INVENTION

Below the resist composition of the invention is described in detail.The singular forms “a,” “an” and “the” include plural referents unlessthe context clearly dictates otherwise.

The notation (Cn-Cm) means a group containing from n to m carbon atomsper group.

It is understood that for some structures represented by chemicalformulae, there can exist enantiomers and diastereomers because of thepresence of asymmetric carbon atoms. In such a case, a single formulacollectively represents all such isomers. The isomers may be used aloneor in admixture.

The resist composition of the invention comprises (A) a resin componentwhich becomes soluble in an alkaline developer under the action of anacid, and (B) a compound capable of generating an acid in response toactinic light or radiation, wherein resin component (A) is a polymercomprising recurring units having the general formula (1).

Herein wherein R¹ is each independently hydrogen, methyl ortrifluoromethyl. R² is hydrogen or CO₂R⁴. R³ is a fluorinatedsubstituent group of 1 to 15 carbon atoms, examples of which aredescribed below. R⁴ is a straight, branched or cyclic monovalenthydrocarbon group of 1 to 20 carbon atoms which may contain aheteroatom(s). Exemplary hydrocarbon groups include methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl,n-hexyl, cyclopentyl, cyclohexyl, ethylcyclopentyl, butylcyclopentyl,ethylcyclohexyl, butylcyclohexyl, adamantyl, ethyladamantyl, andbutyladamantyl, and modified forms of the foregoing in which anycarbon-carbon bond is separated by a hetero atomic group such as —O—,—S—, —SO—, —SO₂—, —NH—, —C(═O)—, —C(═O)O— or —C(═O)NH— or in which anyhydrogen atom is substituted by a functional group such as —OH, —NH₂,—CHO, or —CO₂H. The subscript m is 1 or 2, and n is 1 or 2.

Examples of recurring units having fluorinated substituent groups of 1to 15 carbon atoms represented by R³ are given below, but not limitedthereto.

The subscripts a, b, c, and d indicate ratios of the correspondingrecurring units, and each is a number from more than 0 to less than 1,preferably b is a number from 0.01 to less than 1, and a+b+c+d=1. Thepreferred ratios of recurring units are in the range:

0.05≦a≦0.6, more preferably 0.1≦a≦0.5,

0.05≦b≦0.6, more preferably 0.1≦b≦0.5,

0≦c≦0.5, more preferably 0.05≦c≦0.4, and

0≦d≦0.5, more preferably 0.05≦d≦0.4.

Understandably, a+b+c+d=1 means that in a polymer comprising recurringunits a, b, c, and d, the total of these recurring units a, b, c, and dis 100 mol % relative to the total of entire recurring units.

In formula (1), the unit to be introduced at ratio “a” is a unit inwhich carboxylic acid is protected with a special tertiary alkyl typeprotective group having an oxanorbornane ring. As compared withconventional protective groups, this protective group has very highhydrophilicity and hence, high affinity to a developer liquid. Then, theresin when deprotected by the acid becomes more soluble in the developerand as a result, the LER of the pattern following development isreduced. The oxanorbornane ring-bearing lactone unit to be introduced atratio “c” and the fluorinated functional group unit to be introduced atratio “d” are effective in enhancing developer affinity, possiblybringing a further reduction of LER. The fluorinated functional groupunit is also effective in enhancing the resolution of microscopicchannels and holes. Accordingly the resist composition of the inventioncomprising a resin comprising a combination of a highly hydrophilicprotective group, a highly hydrophilic lactone, and a fluorinatedfunctional group possesses satisfactory resolution performance whilereducing LER to an extremely lower level than prior art resistcompositions.

Exemplary preferred configurations of resin component (A) are givenbelow, but not limited thereto.

The polymer as resin component (A) should preferably have a weightaverage molecular weight (Mw) of 1,000 to 50,000, and more preferably2,000 to 30,000, as measured by gel permeation chromatography (GPC)versus polystyrene standards.

The polymer as resin component (A) may be obtained throughcopolymerization of (meth)acrylic ester derivative monomerscorresponding to the respective recurring units by any well-knowntechnique such as radical polymerization. It is noted that the polymersused in Examples to be described later were synthesized from preselected(meth)acrylic ester derivative monomers by a standard radicalpolymerization technique.

Other Resin Component

In addition to resin component (A) or polymer having formula (1), theresist composition of the invention may further comprise another resincomponent.

The resin component other than resin component (A) that can be added tothe resist composition includes, but is not limited to, polymerscomprising units of the following formula (R1) and/or (R2) and having aweight average molecular weight of 1,000 to 100,000, especially 3,000 to30,000, as measured by GPC versus polystyrene standards.

Herein, R⁰⁰¹ is hydrogen, methyl or CH₂CO₂R⁰⁰³. R⁰⁰² is hydrogen, methylor CO₂R⁰⁰³. R⁰⁰³ is a straight, branched or cyclic C₁-C₁₅ alkyl group,examples of which include methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl,cyclohexyl, ethylcyclopentyl, butylcyclopentyl, ethylcyclohexyl,butylcyclohexyl, adamantyl, ethyladamantyl, and butyladamantyl.

R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon group of 1 to 15 carbonatoms having at least one group selected from among fluorinatedsubstituent groups, carboxyl groups and hydroxyl groups. Examplesinclude hydrogen, carboxyethyl, carboxybutyl, carboxycyclopentyl,carboxycyclohexyl, carboxynorbornyl, carboxyadamantyl, hydroxyethyl,hydroxybutyl, hydroxycyclopentyl, hydroxycyclohexyl, hydroxynorbornyl,hydroxyadamantyl,[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]-cyclohexyl, andbis[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]-cyclohexyl.

At least one of R⁰⁰⁵ to R⁰⁰⁸ represents a carboxyl group or a monovalenthydrocarbon group of 1 to 15 carbon atoms having at least one groupselected from among fluorinated substituent groups, carboxyl groups andhydroxyl groups while the remaining R's independently represent hydrogenor straight, branched or cyclic C₁-C₁₅ alkyl groups. Examples ofsuitable monovalent C₁-C₁₅ hydrocarbon groups having at least one groupselected from among fluorinated substituent groups, carboxyl groups andhydroxyl groups include carboxymethyl, carboxyethyl, carboxybutyl,hydroxymethyl, hydroxyethyl, hydroxybutyl, 2-carboxyethoxycarbonyl,4-carboxybutoxycarbonyl, 2-hydroxyethoxycarbonyl,4-hydroxybutoxycarbonyl, carboxycyclopentyloxycarbonyl,carboxycyclohexyloxycarbonyl, carboxynorbornyloxycarbonyl,carboxyadamantyloxycarbonyl, hydroxycyclopentyloxycarbonyl,hydroxycyclohexyloxycarbonyl, hydroxynorbornyloxycarbonyl,hydroxyadamantyloxycarbonyl,[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]cyclohexyloxycarbonyl,andbis[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)ethyl]cyclohexyloxycarbonyl.Suitable straight, branched or cyclic C₁-C₁₅ alkyl groups are asexemplified for R⁰⁰³.

Two of R⁰⁰⁵ to R⁰⁰⁸ (for example, a pair of R⁰⁰⁵ and R⁰⁰⁶, R⁰⁰⁶ andR⁰⁰⁷, or R⁰⁰⁷ and R⁰⁰⁸) may bond together to form a ring with the carbonatom(s) to which they are attached, and in that event, at least one ofR⁰⁰⁵ to R⁰⁰⁸ is a divalent hydrocarbon group of 1 to 15 carbon atomshaving at least one group selected from fluorinated substituent groups,carboxyl groups and hydroxyl groups, while the remaining R's areindependently single bonds, hydrogen atoms or straight, branched orcyclic C₁-C₁₅ alkyl groups. Suitable divalent C₁-C₁₅ hydrocarbon groupshaving at least one group selected from fluorinated substituent groups,carboxyl groups and hydroxyl groups include those exemplified above asthe monovalent hydrocarbon groups having at least one group selectedfrom fluorinated substituent groups, carboxyl groups and hydroxylgroups, with one hydrogen atom eliminated therefrom. Suitable straight,branched or cyclic C₁-C₁₅ alkyl groups are as exemplified for R⁰⁰³.

R⁰⁰⁹ is a monovalent hydrocarbon group of 3 to 15 carbon atomscontaining a —CO₂— partial structure. Examples include 2-oxooxolan-3-yl,4,4-dimethyl-2-oxooxolan-3-yl, 4-methyl-2-oxooxan-4-yl,2-oxo-1,3-dioxolan-4-ylmethyl, and 5-methyl-2-oxooxolan-5-yl.

At least one of R⁰¹⁰ to R⁰¹³ is a monovalent hydrocarbon group of 2 to15 carbon atoms containing a —CO₂— partial structure, while theremaining R's are independently hydrogen atoms or straight, branched orcyclic C₁-C₁₅ alkyl groups. Illustrative examples of suitable monovalentC₂-C₁₅ hydrocarbon groups containing a —CO₂— partial structure include2-oxooxolan-3-yloxycarbonyl, 4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl,4-methyl-2-oxooxan-4-yloxycarbonyl,2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and5-methyl-2-oxooxolan-5-yloxycarbonyl. Suitable straight, branched orcyclic C₁-C₁₅ alkyl groups are as exemplified for R⁰⁰³.

Two of R⁰¹⁰ to R⁰¹³ (for example, a pair of R⁰¹⁰ and R₀₁₁, R⁰¹¹ andR⁰¹², or R⁰¹² and R⁰¹³) may bond together to form a ring with the carbonatom(s) to which they are attached, and in that event, at least one ofR⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15 carbon atomscontaining a —CO₂— partial structure, while the remaining R's areindependently single bonds, hydrogen atoms or straight, branched orcyclic C₁-C₁₅ alkyl groups. Illustrative examples of suitable divalentC₁-C₁₅ hydrocarbon groups containing a —CO₂— partial structure include1-oxo-2-oxapropane-1,3-diyl, 1,3-dioxo-2-oxapropane-1,3-diyl,1-oxo-2-oxabutane-1,4-diyl, and 1,3-dioxo-2-oxabutane-1,4-diyl, as wellas those exemplified as the monovalent hydrocarbon groups containing a—CO₂— partial structure, with one hydrogen atom eliminated therefrom.Suitable straight, branched or cyclic C₁-C₁₅ alkyl groups are asexemplified for R⁰⁰³.

R⁰¹⁴ is a polycyclic hydrocarbon group having 7 to 15 carbon atoms or analkyl group containing such a polycyclic hydrocarbon group. Examplesinclude norbornyl, bicyclo[3.3.1]nonyl, tricyclo[5.2.1.^(2,6)]decyl,adamantyl, norbornylmethyl, and adamantylmethyl as well as alkyl- orcycloalkyl-substituted forms of the foregoing. R⁰¹⁵ is an acid labilegroup, which will be described later in detail. R⁰¹⁶ is hydrogen ormethyl. R⁰¹⁷ is a straight, branched or cyclic C₁-C₈ alkyl group,examples of which include methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl andcyclohexyl. X is CH₂ or an oxygen atom. Letter k is 0 or 1.

The acid labile group represented by R⁰¹⁵ may be selected from a varietyof such groups to be deprotected with the acid generated from thephotoacid generator. It may be any of well-known acid labile groupscommonly used in prior art resist compositions, especially chemicallyamplified resist compositions. Examples of the acid labile group aregroups of the following general formulae (L1) to (L4), tertiary alkylgroups of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms,trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms,and oxoalkyl groups of 4 to 20 carbon atoms.

Herein, the broken line denotes a valence bond. In formula (L1), R^(L01)and R^(L02) are hydrogen or straight, branched or cyclic alkyl groups of1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. Exemplary alkylgroups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, n-octyl, andadamantyl. R^(L03) is a monovalent hydrocarbon group of 1 to 18 carbonatoms, preferably 1 to 10 carbon atoms, which may contain a heteroatomsuch as oxygen, examples of which include unsubstituted straight,branched or cyclic alkyl groups and substituted forms of such alkylgroups in which some hydrogen atoms are replaced by hydroxyl, alkoxy,oxo, amino, alkylamino or the like. Illustrative examples of thestraight, branched or cyclic alkyl groups are as exemplified above forR^(L01) and R^(L02), and examples of the substituted alkyl groups are asshown below.

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02) andR^(L03) may together form a ring with carbon and oxygen atoms to whichthey are attached. Each of R^(L01), R^(L02) and R^(L03) is a straight orbranched alkylene group of 1 to 18 carbon atoms, preferably 1 to 10carbon atoms when they form a ring.

In formula (L2), R^(L04) is a tertiary alkyl group of 4 to 20 carbonatoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group in whicheach alkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (L1). Exemplary tertiary alkylgroups are tert-butyl, tert-amyl, 1,1-diethylpropyl,2-cyclopentylpropan-2-yl, 2-cyclohexylpropan-2-yl,2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl, 2-(adamantan-1-yl)propan-2-yl,2-(tricyclo[5.2.1.0^(2,6)]decan-8-yl)propan-2-yl,2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecan-3-yl)propan-2-yl,1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl,1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl,2-methyl-2-adamantyl, 2-ethyl-2-adamantyl,8-methyl-8-tricyclo[5.2.1.0^(2,6)]decyl,8-ethyl-8-tricyclo[5.2.1.0^(2,6)]decyl,3-methyl-3-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecyl,3-ethyl-3-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecyl, and the like.Exemplary trialkylsilyl groups are trimethylsilyl, triethylsilyl, anddimethyl-tert-butylsilyl. Exemplary oxoalkyl groups are 3-oxocyclohexyl,4-methyl-2-oxooxan-4-yl, and 5-methyl-2-oxooxolan-5-yl. Letter y is aninteger of 0 to 6.

In formula (L3), R^(L05) is an optionally substituted, straight,branched or cyclic C₁-C₁₀ alkyl group or an optionally substitutedC₆-C₂₀ aryl group. Examples of the optionally substituted alkyl groupsinclude straight, branched or cyclic alkyl groups such as methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl,n-hexyl, cyclopentyl, cyclohexyl, and bicyclo[2.2.1]heptyl, andsubstituted forms of such groups in which some hydrogen atoms arereplaced by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino,alkylamino, cyano, mercapto, alkylthio, sulfo or other groups or inwhich some methylene groups are replaced by oxygen or sulfur atoms.Examples of optionally substituted aryl groups include phenyl,methylphenyl, naphthyl, anthryl, phenanthryl, and pyrenyl. Letter m isequal to 0 or 1, n is equal to 0, 1, 2 or 3, and 2m+n is equal to 2 or3.

In formula (L4), R^(L06) is an optionally substituted, straight,branched or cyclic C₁-C₁₀ alkyl group or an optionally substitutedC₆-C₂₀ aryl group. Examples of these groups are the same as exemplifiedfor R^(L05). R^(L07) to R^(L16) independently represent hydrogen ormonovalent hydrocarbon groups of 1 to 15 carbon atoms. Exemplaryhydrocarbon groups are straight, branched or cyclic alkyl groups such asmethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl,cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl,cyclohexylmethyl, cyclohexylethyl and cyclohexylbutyl, and substitutedforms of these groups in which some hydrogen atoms are replaced byhydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino, alkylamino,cyano, mercapto, alkylthio, sulfo or other groups. Alternatively, two ofR^(L07) to R^(L16) may bond together to form a ring with the carbonatom(s) to which they are attached (for example, a pair of R^(L07) andR^(L08), R^(L07) and R^(L09), R^(L08) and R^(L10), R^(L09) and R^(L10)R^(L11) and R^(L12), R^(L13) and R^(L14), or a similar pair form aring). Each of R^(L07) to R^(L16) represents a divalent C₁-C₁₅hydrocarbon group when they form a ring, examples of which are thoseexemplified above for the monovalent hydrocarbon groups, with onehydrogen atom being eliminated. Two of R^(L07) to R^(L16) which areattached to vicinal carbon atoms may bond together directly to form adouble bond (for example, a pair of R^(L07) and R^(L09), R^(L09) andR^(L15), R^(L13) and R^(L15), or a similar pair).

Of the acid labile groups of formula (L1), the straight and branchedones are exemplified by the following groups.

Of the acid labile groups of formula (L1), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-cyclohexylcyclopentyl, 1-(4-methoxybutyl)cyclopentyl,1-(bicyclo[2.2.1]heptan-2-yl)cyclopentyl,1-(7-oxabicyclo[2.2.1]heptan-2-yl)cyclopentyl, 1-methylcyclohexyl,1-ethylcyclohexyl, 1-methyl-2-cyclopentenyl, 1-ethyl-2-cyclopentenyl,1-methyl-2-cyclohexenyl, and 1-ethyl-2-cyclohexenyl groups.

Of the acid labile groups of formula (L4), those groups of the followingformulae (L4-1) to (L4-4) are preferred.

In formulas (L4-1) to (L4-4), the broken line denotes a bonding site anddirection. R^(L41) is each independently a monovalent hydrocarbon group,typically a straight, branched or cyclic C₁-C₁₀ alkyl group, such asmethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl and cyclohexyl.

For formulas (L4-1) to (L4-4), there can exist enantiomers anddiastereomers. Each of formulae (L4-1) to (L4-4) collectively representsall such stereoisomers. Such stereoisomers may be used alone or inadmixture.

For example, the general formula (L4-3) represents one or a mixture oftwo selected from groups having the following general formulas (L4-3-1)and (L4-3-2).

Similarly, the general formula (L4-4) represents one or a mixture of twoor more selected from groups having the following general formulas(L4-4-1) to (L4-4-4).

Each of formulas (L4-1) to (L4-4), (L4-3-1) and (L4-3-2), and (L4-4-1)to (L4-4-4) collectively represents an enantiomer thereof and a mixtureof enantiomers.

It is noted that in the above formulas (L4-1) to (L4-4), (L4-3-1) and(L4-3-2), and (L4-4-1) to (L4-4-4), the bond direction is on the exoside relative to the bicyclo[2.2.1]heptane ring, which ensures highreactivity for acid catalyzed elimination reaction (see JP-A2000-336121). In preparing these monomers having a tertiary exo-alkylgroup of bicyclo[2.2.1]heptane structure as a substituent group, theremay be contained monomers substituted with an endo-alkyl group asrepresented by the following formulas (L4-1-endo) to (L4-4-endo). Forgood reactivity, an exo proportion of at least 50 mol % is preferred,with an exo proportion of at least 80 mol % being more preferred.

Illustrative examples of the acid labile group of formula (L4) are givenbelow.

Examples of the tertiary C₄-C₂₀ alkyl groups, trialkylsilyl groups inwhich each alkyl moiety has 1 to 6 carbon atoms, and C₄-C₂₀ oxoalkylgroups are as exemplified for R^(L04) and the like.

In formula (R2), R⁰¹⁶ is hydrogen or methyl. R⁰¹⁷ is a straight,branched or cyclic C₁-C₈ alkyl group.

In formulae (R1) and (R2), letters a1′, a2′, a3′, b1′, b2′, b3′, c1′,c2′, c3′, d1′, d2′, d3′, and e′ are numbers from 0 to less than 1,satisfying a1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1; f′, g′,h′, i′, j′, o′, and p′ are numbers from 0 to less than 1, satisfyingf′+g′+h′+i′+j′+o′+p′=1; x′, y′ and z′ are each an integer of 0 to 3,satisfying 1≦x′+y′+z′≦5 and 1≦y′+z′≦3.

With respect to the recurring units of formula (R1) and (R2), units ofmore than one type may be incorporated at the same time. Incorporationof units of more than one type enables to adjust the performance of aresist material in which the resulting polymer is formulated.

Understandably, the sum of respective units=1 means that in a polymercomprising recurring units, the total of the indicated recurring unitsis 100 mol % relative to the total of entire recurring units.

Examples of the recurring units incorporated at compositional ratio a1′in formula (R1) and the recurring units incorporated at compositionalratio f′ in formula (R2) are given below, but not limited thereto.

Examples of the recurring units incorporated at compositional ratio b1′in formula (R1) are given below, but not limited thereto.

Examples of the recurring units incorporated at compositional ratio d1′in formula (R1) and the recurring units incorporated at compositionalratio g′ in formula (R2) are given below, but not limited thereto.

Exemplary polymers comprising recurring units incorporated atcompositional ratios a1′, b1′, c1′, and d1′ in formula (R1) are shownbelow, but not limited thereto.

Exemplary polymers comprising recurring units incorporated atcompositional ratios a2′, b2′, c2′, d2′ and e′ in formula (R1) are shownbelow, but not limited thereto.

Exemplary polymers comprising recurring units incorporated atcompositional ratios a3′, b3′, c3′, and d3′ in formula (R1) are shownbelow, but not limited thereto.

Examples of polymers having formula (R2) are shown below, but notlimited thereto.

The other polymer is blended in an amount of preferably 0 to 80 parts,more preferably 0 to 60 parts, and even more preferably 0 to 50 parts byweight, provided that the total of the resin component (A) and the otherpolymer is 100 parts by weight. When blended, the amount of the otherpolymer is preferably at least 20 parts, more preferably at least 30parts by weight. Too much amounts of the other polymer may prevent theresin component (A) from exerting its own effect, probably resulting ina lower resolution and degraded pattern profile. The other polymer isnot limited to one type and a mixture of two or more other polymers maybe added. The use of plural polymers allows for easy adjustment ofresist properties.

Acid Generator

The resist composition of the invention also comprises (B) a compoundwhich generates an acid in response to actinic light or radiation.Component (B) may be any compound which generates an acid upon exposureto high-energy radiation and specifically, any of well-known photoacidgenerators which are commonly used in prior art resist compositions,especially chemically amplified resist compositions. Suitable photoacidgenerators include sulfonium salts, iodonium salts,sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate acidgenerators. Exemplary acid generators are given below while they may beused alone or in admixture of two or more.

Sulfonium salts are salts of sulfonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary sulfonium cations includetriphenylsulfonium, (4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxyphenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium,(3-tert-butoxyphenyl)diphenylsulfonium,bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxyphenyl)sulfonium,(3,4-di-tert-butoxyphenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium,tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium,dimethyl-2-naphthylsulfonium, 4-hydroxyphenyldimethylsulfonium,4-methoxyphenyldimethylsulfonium, trimethylsulfonium,2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium,tribenzylsulfonium, diphenylmethylsulfonium, dimethylphenylsulfonium,2-oxo-2-phenylethylthiacyclopentanium,4-n-butoxynaphthyl-1-thiacyclopentanium, and2-n-butoxynaphthyl-1-thiacyclopentanium. Exemplary sulfonates includetrifluoromethanesulfonate, pentafluoroethanesulfonate,nonafluorobutanesulfonate, dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4′-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. Atypical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Sulfonium salts based on combinationof the foregoing examples are included.

Iodonium salts are salts of iodonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary iodonium cations are aryliodoniumcations including diphenyliodinium, bis(4-tert-butylphenyl)iodonium,4-tert-butoxyphenylphenyliodonium, and 4-methoxyphenylphenyliodonium.Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. Atypical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Iodonium salts based on combinationof the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethanecompounds and sulfonylcarbonyldiazomethane compounds such asbis(ethylsulfonyl)diazomethane, bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)diazomethane,bis(4-acetyloxyphenylsulfonyl)diazomethane,bis(4-methanesulfonyloxyphenylsulfonyl)diazomethane,bis(4-(4-toluenesulfonyloxy)phenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyldiazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

N-sulfonyloxyimide photoacid generators include combinations of imidestructures with sulfonates. Exemplary imide structures are succinimide,naphthalene dicarboxylic acid imide, phthalimide, cyclohexyldicarboxylicacid imide, 5-norbornene-2,3-dicarboxylic acid imide, and7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid imide. Exemplarysulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Benzoinsulfonate photoacid generators include benzoin tosylate, benzoinmesylate, and benzoin butanesulfonate.

Pyrogallol trisulfonate photoacid generators include pyrogallol,phloroglucinol, catechol, resorcinol, and hydroquinone, in which all thehydroxyl groups are substituted by trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Nitrobenzyl sulfonate photoacid generators include 2,4-dinitrobenzylsulfonates, 2-nitrobenzyl sulfonates, and 2,6-dinitrobenzyl sulfonates,with exemplary sulfonates including trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Also useful are analogous nitrobenzyl sulfonate compounds in which thenitro group on the benzyl side is substituted by a trifluoromethylgroup.

Sulfone photoacid generators include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

Photoacid generators in the form of glyoxime derivatives are describedin Japanese Patent No. 2,906,999 and JP-A 9-301948 and includebis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-O-(methanesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,bis-O-(2,2,2-trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-O-(10-camphorsulfonyl)-α-dimethylglyoxime,bis-O-(benzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-trifluoromethylbenzenesulfonyl)-α-dimethylglyoxime,bis-O-(xylenesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-nioxime,bis-O-(2,2,2-trifluoroethanesulfonyl)-nioxime,bis-O-(10-camphorsulfonyl)-nioxime, bis-O-(benzenesulfonyl)-nioxime,bis-O-(p-fluorobenzenesulfonyl)-nioxime,bis-O-(p-trifluoromethylbenzenesulfonyl)-nioxime, andbis-O-(xylenesulfonyl)-nioxime.

Also included are the oxime sulfonates described in U.S. Pat. No.6,004,724, for example,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,etc. Also included are the oxime sulfonates described in U.S. Pat. No.6,916,591, for example,(5-(4-(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrileand(5-(2,5-bis(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile.

Also included are the oxime sulfonates described in U.S. Pat. No.6,261,738 and JP-A 2000-314956, for example,2,2,2-trifluoro-1-phenyl-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(4-methoxyphenylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanoneoxime-O-(2,4,6-trimethylphenylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-(methylsulfonate);2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylthiophenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,3,3,4,4,4-heptafluoro-1-phenyl-butanoneoxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-10-camphorylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(1-naphthyl)-sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2,4,6-trimethylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-methyl-sulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-dodecylphenyl)-sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-l-(4-thiomethylphenyl)-ethanoneoxime-O-(4-dodecylphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylphenyl)ethanone oxime-O-phenylsulfonate;2,2,2-trifluoro-1-(4-chlorophenyl)-ethanone oxime-O-phenylsulfonate;2,2,3,3,4,4,4-heptafluoro-1-(phenyl)-butanoneoxime-O-(10-camphoryl)sulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-methylsulfonate;2,2,2-trifluoro-1-[4-(phenyl-1,4-dioxa-but-1-yl)phenyl]-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1- [4-benzylphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylsulfonylphenyl]-ethanoneoxime-O-propylsulfonate;1,3-bis[1-(4-phenoxyphenyl)-2,2,2-trifluoroethanoneoxime-O-sulfonyl]phenyl;2,2,2-trifluoro-1-[4-methylsulfonyloxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylcarbonyloxyphenyl)-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[6H,7H-5,8-dioxonaphth-2-yl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methoxycarbonylmethoxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-(methoxycarbonyl)-(4-amino-1-oxa-pent-1-yl)-phenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[3,5-dimethyl-4-ethoxyphenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzyloxyphenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[2-thiophenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[1-dioxa-thiophen-2-yl)]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(trifluoromethanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(trifluoromethanesulfonate);2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-propane-sulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(1-propanesulfonate); and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-butanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(1-butanesulfonate). Also included are the oxime sulfonatesdescribed in U.S. Pat. No. 6,916,591, for example,2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(4-(4-methylphenylsulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(4-(4-methylphenylsulfonyloxy)phenylsulfonate) and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)phenylsulfonate).

Also included are the oxime sulfonates described in JP-A 9-95479 andJP-A 9-230588 and the references cited therein, for example,α-(p-toluenesulfonyloxyimino)-phenylacetonitrile,α-(p-chlorobenzenesulfonyloxyimino)-phenylacetonitrile,α-(4-nitrobenzenesulfonyloxyimino)-phenylacetonitrile,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-phenylacetonitrile,α-(benzenesulfonyloxyimino)-4-chlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-2,4-dichlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-2,6-dichlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-4-methoxyphenylacetonitrile,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxyphenylacetonitrile,α-(benzenesulfonyloxyimino)-2-thienylacetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)-phenylacetonitrile,α-[(4-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-3-thienylacetonitrile,α-(methylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenylacetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenylacetonitrile, andα-(n-butylsulfonyloxyimino)-1-cyclohexenylacetonitrile.

Also included are oxime sulfonates having the formula:

wherein R^(s1) is a substituted or unsubstituted haloalkylsulfonyl orhalobenzenesulfonyl group of 1 to 10 carbon atoms, R^(s2) is a haloalkylgroup of 1 to 11 carbon atoms, and Ar^(s1) is substituted orunsubstituted aromatic or hetero-aromatic group, examples of which aredescribed, for example, in WO 2004/074242.

Examples include2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene,2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-fluorene,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-4-biphenyl,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-4-biphenyl,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-4-biphenyl.

Suitable bisoxime sulfonates include those described in JP-A 9-208554,for example,bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(benzenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(methanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(butanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(10-camphorsulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(trifluoromethanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(4-methoxybenzenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(benzenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(methanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(butanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(10-camphorsulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(trifluoromethanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(4-methoxybenzenesulfonyloxy)imino)-m-phenylenediacetonitrile,etc.

Of these, preferred photoacid generators are sulfonium salts,bissulfonyldiazomethanes, N-sulfonyloxyimides, oxime-O-sulfonates andglyoxime derivatives. More preferred photoacid generators are sulfoniumsalts, bissulfonyldiazomethanes, N-sulfonyloxyimides, andoxime-O-sulfonates. Typical examples include triphenylsulfoniump-toluenesulfonate, triphenylsulfonium camphorsulfonate,triphenylsulfonium pentafluorobenzenesulfonate, triphenylsulfoniumnonafluorobutanesulfonate, triphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, triphenylsulfonium2,4,6-triisopropylbenzenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniump-toluenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniumcamphorsulfonate, 4-tert-butoxyphenyldiphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, tris(4-methylphenyl)sulfoniumcamphorsulfonate, tris(4-tert-butylphenyl)sulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium nonafluoro-1-butanesulfonate,4-tert-butylphenyldiphenylsulfoniumpentafluoroethylperfluorocyclohexanesulfonate,4-tert-butylphenyldiphenylsulfonium perfluoro-1-octanesulfonate,triphenylsulfonium 1,1-difluoro-2-naphthyl-ethanesulfonate,triphenylsulfonium1,1,2,2-tetrafluoro-2-(norbornan-2-yl)-ethanesulfonate,bis(tert-butylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(4-tert-butylphenylsulfonyl)diazomethane,N-camphorsulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,N-p-toluenesulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-fluorene.

In the resist composition, an appropriate amount of the photoacidgenerator (B) is, but not limited to, 0.1 to 20 parts, and especially0.1 to 10 parts by weight per 100 parts by weight of the base polymer(i.e., resin component (A) and optional other resin component). Too higha proportion of the photoacid generators may give rise to problems ofdegraded resolution and foreign matter upon development and resist filmpeeling. The photoacid generator (B) may be used alone or in admixtureof two or more. The transmittance of the resist film can be controlledby using a photoacid generator having a low transmittance at theexposure wavelength and adjusting the amount of the photoacid generatoradded.

In the resist composition, there may be added a compound which isdecomposed with an acid to generate another acid, that is,acid-amplifier compound. For these compounds, reference should be madeto J. Photopolym. Sci. and Tech., 8, 43-44, 45-46 (1995), and ibid., 9,29-30 (1996).

Examples of the acid-amplifier compound includetert-butyl-2-methyl-2-tosyloxymethyl acetoacetate and2-phenyl-2-(2-tosyloxyethyl)-1,3-dioxolane, but are not limited thereto.Of well-known photoacid generators, many of those compounds having poorstability, especially poor thermal stability exhibit an acidamplifier-like behavior.

In the resist composition, an appropriate amount of the acid-amplifiercompound is 0 to 2 parts, and especially 0 to 1 part by weight per 100parts by weight of the base polymer. Excessive amounts of theacid-amplifier compound make diffusion control difficult, leading todegradation of resolution and pattern profile.

In addition to components (A) and (B), the resist composition mayfurther comprise (C) an organic solvent and optionally (D) an organicnitrogen-containing compound, (E) a surfactant, and (F) othercomponents.

Organic Solvent

The organic solvent (C) used herein may be any organic solvent in whichthe base resin, acid generator, and additives are soluble. Illustrative,non-limiting, examples of the organic solvent include ketones such ascyclohexanone and methyl amyl ketone; alcohols such as 3-methoxybutanol,3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether,ethylene glycol monomethyl ether, propylene glycol monoethyl ether,ethylene glycol monoethyl ether, propylene glycol dimethyl ether, anddiethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate (PGMEA), propylene glycol monoethyl etheracetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as γ-butyrolactone. These solvents may beused alone or in combinations of two or more thereof. Of the aboveorganic solvents, it is recommended to use diethylene glycol dimethylether, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate,and mixtures thereof because the acid generator is most soluble therein.

An appropriate amount of the organic solvent used is about 200 to 3,000parts, especially about 400 to 2,500 parts by weight per 100 parts byweight of the base polymer.

Nitrogen-Containing Compound

In the resist composition, an organic nitrogen-containing compound orcompounds may be compounded as component (D). The organicnitrogen-containing compound used herein is preferably a compoundcapable of suppressing the rate of diffusion when the acid generated bythe acid generator diffuses within the resist film. The inclusion oforganic nitrogen-containing compound holds down the rate of aciddiffusion within the resist film, resulting in better resolution. Inaddition, it suppresses changes in sensitivity following exposure andreduces substrate and environment dependence, as well as improving theexposure latitude and the pattern profile.

The organic nitrogen-containing compound used herein may be any ofwell-known organic nitrogen-containing compounds which are commonly usedin prior art resist compositions, especially chemically amplified resistcompositions. Suitable organic nitrogen-containing compounds includeprimary, secondary, and tertiary aliphatic amines, mixed amines,aromatic amines, heterocyclic amines, nitrogen-containing compoundshaving carboxyl group, nitrogen-containing compounds having sulfonylgroup, nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, alcoholicnitrogen-containing compounds, amide derivatives, imide derivatives, andcarbamate derivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,isobutylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine, diisopropylamine,di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine,dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine,dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, triisopropylamine, tri-n-butylamine,triisobutylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,4-pyrrolidinopyridine, 2-(1-ethylpropyl)pyridine, aminopyridine, anddimethylaminopyridine), pyridazine derivatives, pyrimidine derivatives,pyrazine derivatives, pyrazoline derivatives, pyrazolidine derivatives,piperidine derivatives, piperazine derivatives, morpholine derivatives,indole derivatives, isoindole derivatives, 1H-indazole derivatives,indoline derivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds having carboxyl groupinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable nitrogen-containing compounds having sulfonyl group include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, and alcoholicnitrogen-containing compounds include 2-hydroxypyridine, aminocresol,2,4-quinolinediol, 3-indolemethanol hydrate, monoethanolamine,diethanolamine, triethanolamine, N-ethyldiethanolamine,N,N-diethylethanolamine, triisopropanolamine, 2,2′-iminodiethanol,2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol,4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine,1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]piperazine,piperidine ethanol, 1-(2-hydroxyethyl)pyrrolidine,1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol,3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol,3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol,N-(2-hydroxyethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide.Examples of suitable amide derivatives include formamide,N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, propionamide, benzamide, and1-cyclohexylpyrrolidone. Suitable imide derivatives include phthalimide,succinimide, and maleimide. Suitable carbamate derivatives includeN-t-butoxycarbonyl-N,N-dicyclohexylamine,N-t-butoxycarbonylbenzimidazole and oxazolidinone.

In addition, organic nitrogen-containing compounds of the followinggeneral formula (B)-1 may also be included alone or in admixture.

N(X)_(n)(Y)_(3-n)   (B)-1

In the formula, n is equal to 1, 2 or 3; side chain Y is independentlyhydrogen or a straight, branched or cyclic C₁-C₂₀ alkyl group which maycontain an ether or hydroxyl group; and side chain X is independentlyselected from groups of the following general formulas (X1) to (X3), andtwo or three X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched C₁-C₄ alkylene groups; R³⁰¹ and R³⁰⁴ are independentlyhydrogen, or straight, branched or cyclic C₁-C₂₀ alkyl groups which maycontain at least one hydroxyl, ether, ester group or lactone ring; R³⁰³is a single bond or a straight or branched C₁-C₄ alkylene group; andR³⁰⁶ is a straight, branched or cyclic C₁-C₂₀ alkyl group which maycontain at least one hydroxyl, ether, ester group or lactone ring.

Illustrative examples of the compounds of formula (B)-1 includetris(2-methoxymethoxyethyl)amine, tris(2-(2-methoxyethoxy)ethyl)amine,tris{2-(2-methoxyethoxymethoxy)ethyl)amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris(2-(1-ethoxypropoxy)ethyl)amine,tris[2-[2-(2-hydroxyethoxy)ethoxy)ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-l-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis(2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andp-(diethylamino)-δ-valerolactone.

Also useful are one or more organic nitrogen-containing compounds havingcyclic structure represented by the following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branched C₂-C₂₀alkylene group which may contain one or more carbonyl, ether, ester orsulfide groups.

Illustrative examples of the organic nitrogen-containing compoundshaving formula (B)-2 include 1-[2-(methoxymethoxy)ethyl]pyrrolidine,1-[2-(methoxymethoxy)ethyl]piperidine,4-[2-(methoxymethoxy)ethyl]morpholine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethylacetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate,2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate,2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethylmethoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine,1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate,methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate,2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,tetrahydrofurfuryl 3-morpholinopropionate, glycidyl3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate,2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl3-morpholinopropionate, cyclohexyl 3-piperidinopropionate,α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone,β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methylpiperidinoacetate, methyl morpholinoacetate, methylthiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, 2-methoxyethylmorpholinoacetate, 2-morpholinoethyl 2-methoxyacetate, 2-morpholinoethyl2-(2-methoxyethoxy)acetate, 2-morpholinoethyl2-[2-(2-methoxyethoxy)ethoxy]acetate, 2-morpholinoethyl hexanoate,2-morpholinoethyl octanoate, 2-morpholinoethyl decanoate,2-morpholinoethyl laurate, 2-morpholinoethyl myristate,2-morpholinoethyl palmitate, and 2-morpholinoethyl stearate.

Also, one or more organic nitrogen-containing compounds having cyanogroup represented by the following general formulae (B)-3 to (B)-6 maybe blended.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are eachindependently a straight or branched C₁-C₄ alkylene group.

Illustrative examples of the organic nitrogen-containing compoundshaving cyano represented by formulae (B)-3 to (B)-6 include3-(diethylamino)propiononitrile,N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methylN-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methylN-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile,N,N-bis(2-hydroxyethyl)aminoacetonitrile,N,N-bis(2-acetoxyethyl)aminoacetonitrile,N,N-bis(2-formyloxyethyl)aminoacetonitrile,N,N-bis(2-methoxyethyl)aminoacetonitrile,N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methylN-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methylN-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile,N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile,1-piperidinepropiononitrile, 4-morpholinepropiononitrile,1-pyrrolidineacetonitrile, 1-piperidineacetonitrile,4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate,cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl3-diethylaminopropionate, 2-cyanoethylN,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate,2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl4-morpholinepropionate.

Also included are organic nitrogen-containing compounds having animidazole structure and a polar functional group, represented by thegeneral formula (B)-7.

Herein, R³¹⁰ is a straight, branched or cyclic C₂-C₂₀ alkyl groupbearing at least one polar functional group selected from amonghydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetalgroups; R³¹¹, R³¹² and R³¹³ are each independently a hydrogen atom, astraight, branched or cyclic C₁-C₁₀ alkyl group, aryl group or aralkylgroup.

Also included are organic nitrogen-containing compounds having abenzimidazole structure and a polar functional group, represented by thegeneral formula (B)-8.

Herein, R³¹⁴ is a hydrogen atom, a straight, branched or cyclic C₁-C₁₀alkyl group, aryl group or aralkyl group. R³¹⁵ is a polar functionalgroup-bearing, straight, branched or cyclic C₁-C₂₀ alkyl group, and thealkyl group contains as the polar functional group at least one groupselected from among ester, acetal and cyano groups, and may additionallycontain at least one group selected from among hydroxyl, carbonyl,ether, sulfide and carbonate groups.

Further included are heterocyclic nitrogen-containing compounds having apolar functional group, represented by the general formulae (B)-9 and(B)-10.

Herein, A is a nitrogen atom or ≡C—R³²², B is a nitrogen atom or≡C—R³²³, R³¹⁶ is a straight, branched or cyclic C₂-C₂₀ alkyl groupbearing at least one polar functional group selected from amonghydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetalgroups; R³¹⁷, R³¹⁸, R³¹⁹ and R³²⁰ are each independently a hydrogenatom, a straight, branched or cyclic C₁-C₁₀ alkyl group or aryl group,or a pair of R³¹⁷ and R³¹⁸ and a pair of R³¹⁹ and R³²⁰, taken together,may form a benzene, naphthalene or pyridine ring; R³²¹ is a hydrogenatom, a straight, branched or cyclic C₁-C₁₀ alkyl group or aryl group;R³²² and R³²³ each are a hydrogen atom, a straight, branched or cyclicC₁-C₁₀ alkyl group or aryl group, or a pair of R³²¹ and R³²³, takentogether, may form a benzene or naphthalene ring.

Also included are organic nitrogen-containing compounds of aromaticcarboxylic ester structure having the general formulae (B)-11 to (B)-14.

Herein R³²⁴ is a C₆-C₂₀ aryl group or C₄-C₂₀ hetero-aromatic group, inwhich some or all of hydrogen atoms may be replaced by halogen atoms,straight, branched or cyclic C₁-C₂₀ alkyl groups, C₆-C₂₀ aryl groups,C₁-C₂₀ aralkyl groups, C₁-C₁₀ alkoxy groups, C₁-C₁₀ acyloxy groups orC₁-C₁₀ alkylthio groups. R³²⁵ is CO₂R³²⁶, OR³²⁷ or cyano group. R³²⁶ isa C₁-C₁₀ alkyl group, in which some methylene groups may be replaced byoxygen atoms. R³²⁷ is a C₁-C₁₀ alkyl or acyl group, in which somemethylene groups may be replaced by oxygen atoms. R³²⁸ is a single bond,methylene, ethylene, sulfur atom or —O(CH₂CH₂O)_(n)— group wherein n is0, 1, 2, 3 or 4. R³²⁹ is hydrogen, methyl, ethyl or phenyl. X is anitrogen atom or CR³³⁰. Y is a nitrogen atom or CR³³¹. Z is a nitrogenatom or CR³³². R³³⁰, R³³¹ and R³³² are each independently hydrogen,methyl or phenyl. Alternatively, a pair of R³³⁰ and R³³¹ or a pair ofR³³¹ and R³³² may bond together to form a C₆-C₂₀ aromatic ring or C₂-C₂₀hetero-aromatic ring.

Further included are organic nitrogen-containing compounds of7-oxanorbornane-2-carboxylic ester structure having the general formula(B)-15.

Herein R³³³ is hydrogen or a straight, branched or cyclic C₁-C₁₀ alkylgroup. R³³⁴ and R³³⁵ are each independently a C₁-C₂₀ alkyl group, C₆-C₂₀aryl group or C₇-C₂₀ aralkyl group, which may contain one or more polarfunctional groups selected from among ether, carbonyl, ester, alcohol,sulfide, nitrile, amine, imine, and amide and in which some hydrogenatoms may be replaced by halogen atoms. R³³⁴ and R³³⁵, taken together,may form a heterocyclic or hetero-aromatic ring of 2 to 20 carbon atoms.

The organic nitrogen-containing compounds may be used alone or inadmixture of two or more. The organic nitrogen-containing compound ispreferably formulated in an amount of 0.001 to 4 parts, and especially0.01 to 2 parts by weight, per 100 parts by weight of the base polymer.Less than 0.001 part of the nitrogen-containing compound achieves no orlittle addition effect whereas more than 4 parts would result in too lowa sensitivity.

Other Components

The resist composition of the invention may include optionalingredients, for example, a surfactant which is commonly used forimproving the coating characteristics. Optional ingredients may be addedin conventional amounts so long as this does not compromise the objectsof the invention.

Nonionic surfactants are preferred, examples of which includeperfluoroalkylpolyoxyethylene ethanols, fluorinated alkyl esters,perfluoroalkylamine oxides, perfluoroalkyl EO-addition products, andfluorinated organosiloxane compounds. Useful surfactants arecommercially available under the trade names Fluorad FC-430 and FC-431from Sumitomo 3M, Ltd., Surflon S-141, S-145, KH-10, KH-20, KH-30 andKH-40 from Asahi Glass Co., Ltd., Unidyne DS-401, DS-403 and DS-451 fromDaikin Industry Co., Ltd., Megaface F-8151 from Dai-Nippon Ink &Chemicals, Inc., and X-70-092 and X-70-093 from Shin-Etsu Chemical Co.,Ltd. Preferred surfactants are Fluorad FC-430 from Sumitomo 3M, Ltd.,KH-20 and KH-30 from Asahi Glass Co., Ltd., and X-70-093 from Shin-EtsuChemical Co., Ltd.

Optionally, a polymer may be added to the resist composition of theinvention which will be locally distributed at the top of a coating andfunctions to adjust a hydrophilic/hydrophobic balance at the surface, toenhance water repellency, or to prevent low-molecular-weight componentsfrom flowing into or out of the coating when the coating comes incontact with water or similar liquids. The functional polymer may beadded in customary amounts as long as it does not compromise the objectsof the invention.

Preferred examples of the functional polymer which will be localized atthe coating top include polymers and copolymers comprising fluorinatedunits of one or more types, and copolymers comprising fluorinated unitsand other units. Illustrative examples of suitable fluorinated units andother units are shown below, but not limited thereto.

The functional polymer which will be localized at the coating top shouldpreferably have a weight average molecular weight of 1,000 to 50,000,more preferably 2,000 to 20,000, as measured by GPC versus polystyrenestandards. Outside the range, the polymer may have insufficientsurface-modifying effect or cause development defects.

To the resist composition of the invention, other components such asdissolution regulators, carboxylic acid compounds and acetylene alcoholderivatives may be added if necessary. Optional components may be addedin conventional amounts so long as this does not compromise the objectsof the invention.

The dissolution regulator which can be added to the resist compositionis a compound having on the molecule at least two phenolic hydroxylgroups, in which an average of from 0 to 100 mol % of all the hydrogenatoms on the phenolic hydroxyl groups are replaced by acid labile groupsor a compound having on the molecule at least one carboxyl group, inwhich an average of 50 to 100 mol % of all the hydrogen atoms on thecarboxyl groups are replaced by acid labile groups, both the compoundshaving a weight average molecular weight within a range of 100 to 1,000,and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having a carboxyl group include those offormulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl group, for example, hydrogen, methyl,ethyl, butyl, propyl, ethynyl and cyclohexyl.

R²⁰³ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl group,or —(R²⁰⁷)_(h)—COOH wherein R²⁰⁷ is a straight or branched C₁-C₁₀alkylene, for example, those exemplified for R²⁰¹ and R²⁰² and —COOH and—CH₂COOH.

R²⁰⁴ is —(CH₂)_(i)— wherein i=2 to 10, C₆-C₁₀ arylene, carbonyl,sulfonyl, an oxygen atom, or a sulfur atom, for example, ethylene,phenylene, carbonyl, sulfonyl, oxygen atom or sulfur atom.

R²⁰⁵ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl, sulfonyl, anoxygen atom, or a sulfur atom, for example, methylene and thoseexemplified for R²⁰⁴.

R²⁰⁶ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or aphenyl or naphthyl group in which at least one hydrogen atom issubstituted by a hydroxyl group, for example, hydrogen, methyl, ethyl,butyl, propyl, ethynyl, cyclohexyl, hydroxyl-substituted phenyl, andhydroxyl-substituted naphthyl.

R²⁰⁸ is hydrogen or hydroxyl.

The letter j is an integer from 0 to 5; u and h are each 0 or 1; s, t,s′, t′, s″, and t″ are each numbers which satisfy s+t=8, s′+t′=5, ands″+t″=4, and are such that each phenyl structure has at least onehydroxyl group; and α is a number such that the compounds of formula(D8) or (D9) have a weight average molecular weight of from 100 to1,000.

Exemplary acid labile groups on the dissolution regulator include avariety of such groups, typically groups of the general formulae (L1) to(L4), tertiary C₄-C₂₀ alkyl groups, trialkylsilyl groups in which eachof the alkyls has 1 to 6 carbon atoms, and C₄-C₂₀ oxoalkyl groups.Examples of the respective groups are as previously described.

The dissolution regulator may be formulated in an amount of 0 to 50parts, preferably 0 to 40 parts, and more preferably 0 to 30 parts byweight, per 100 parts by weight of the base polymer, and may be usedsingly or as a mixture of two or more thereof. The use of more than 50parts of the dissolution regulator would lead to slimming of thepatterned film, and thus a decline in resolution.

The dissolution regulator can be synthesized by introducing acid labilegroups into a compound having phenolic hydroxyl or carboxyl groups inaccordance with an organic chemical formulation.

In the resist composition, a carboxylic acid compound may be blended.The carboxylic acid compound used herein may be one or more compoundsselected from Groups I and II below, but is not limited thereto.Including this compound improves the PED stability of the resist andameliorates edge roughness on nitride film substrates.

Group I:

Compounds of general formulas (A1) to (A10) below in which some or allof the hydrogen atoms on the phenolic hydroxyl groups are replaced by—R⁴⁰¹—COOH (wherein R⁴⁰¹ is a straight or branched C₁-C₁₀ alkylenegroup), and in which the molar ratio C/(C+D) of phenolic hydroxyl groups(C) to ≡C—COOH groups (D) in the molecule is from 0.1 to 1.0.

Group II:

Compounds of general formulas (A11) to (A15) below.

In these formulas, R⁴⁰² and R⁴⁰³ are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl. R⁴⁰⁴ is hydrogen, a straight orbranched C₁-C₈ alkyl or alkenyl, or a —(R⁴⁰⁹)_(h1)—COOR′ group whereinR′ is hydrogen or —R⁴⁰⁹—COOH.

R⁴⁰⁵ is —(CH₂)_(i)— (wherein i is 2 to 10), a C₆-C₁₀ arylene, carbonyl,sulfonyl, an oxygen atom, or a sulfur atom. R⁴⁰⁶ is a C₁-C₁₀ alkylene, aC₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom.R⁴⁰⁷ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or ahydroxyl-substituted phenyl or naphthyl. R⁴⁰⁸ is hydrogen or methyl.R⁴⁰⁹ is a straight or branched C₁-C₁₀ alkylene. R⁴¹⁰ is hydrogen, astraight or branched C₁-C₈ alkyl or alkenyl, or a —R⁴¹¹—COOH groupwherein R⁴¹¹ is a straight or branched C₁-C₁₀ alkylene. R⁴¹² is hydrogenor hydroxyl.

The letter j is a number from 0 to 3; s1, t1, s2, t2, s3, t3, s4, and t4are each numbers which satisfy s1+t1=8, s2+t2=5, s3+t3=4, and s4+t4=6,and are such that each phenyl structure has at least one hydroxyl group;s5 and t5 are numbers which satisfy s5≧0, t5≧0, and s5+t5=5; u1 is anumber from 1 to 4; h1 is a number from 0 to 4; κ is a number such thatthe compound of formula (A6) may have a weight average molecular weightof 1,000 to 5,000; and λ is a number such that the compound of formula(A7) may have a weight average molecular weight of 1,000 to 10,000.

Illustrative, non-limiting examples of the compound having a carboxylgroup include compounds of the general formulas AI-1 to AI-14 and AII-1to AII-10 below.

In the above formulas, R″ is hydrogen or a —CH₂COOH group such that the—CH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, κand λ are as defined above.

The compound having a ≡C—COOH group may be used singly or ascombinations of two or more thereof. The compound having a ≡C—COOH groupis added in an amount ranging from 0 to 5 parts, preferably 0.1 to 5parts, more preferably 0.1 to 3 parts, further preferably 0.1 to 2 partsby weight, per 100 parts by weight of the base polymer. More than 5parts of the compound can reduce the resolution of the resistcomposition.

Preferred examples of the acetylene alcohol derivative which can beadded to the resist composition include those having the general formula(S1) or (S2) below.

In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴, and R⁵⁰⁵ are each hydrogen or astraight, branched or cyclic C₁-C₈ alkyl; and X and Y are each 0 or apositive number, satisfying 0≦X≦30, 0≦Y≦30, and 0≦X+Y≦40.

Preferable examples of the acetylene alcohol derivative include Surfynol61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H, Surfynol104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, and Surfynol485 from Air Products and Chemicals Inc., and Surfynol E1004 fromNisshin Chemical Industries Ltd.

The acetylene alcohol derivative is preferably added in an amount of 0to 2 parts, more preferably 0.01 to 2 parts, and even more preferably0.02 to 1 part by weight per 100 parts by weight of the base polymer inthe resist composition. More than 2 parts by weight would result in aresist having a low resolution.

Process

Pattern formation using the resist composition of the invention may beperformed by well-known lithography processes. The process generallyinvolves coating, heat treatment (or prebaking), exposure, heattreatment (post-exposure baking, PEB), and development. If necessary,any additional steps may be added.

For pattern formation, the resist composition is first applied onto asubstrate (on which an integrated circuit is to be formed, e.g., Si,SiO₂, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective coating,Cr, CrO, CrON, MoSi, etc.) by a suitable coating technique such as spincoating, roll coating, flow coating, dip coating, spray coating ordoctor coating. The coating is prebaked on a hot plate at a temperatureof 60 to 150° C. for about 1 to 10 minutes, preferably 80 to 140° C. for1 to 5 minutes. The resulting resist film is generally 0.01 to 2.0 μmthick.

A relationship of a reduced thickness of resist film to an etchselectivity ratio between resist film and processable substrate imposesseverer limits on the process. Under consideration is the tri-layerprocess in which a resist layer, a silicon-containing intermediatelayer, an undercoat layer having a high carbon density and high etchresistance, and a processable substrate are laminated in sequence fromtop to bottom. On etching with oxygen gas, hydrogen gas, ammonia gas orthe like, a high etch selectivity ratio is available between thesilicon-containing intermediate layer and the undercoat layer, whichallows for thickness reduction of the silicon-containing intermediatelayer. A relatively high etch selectivity ratio is also availablebetween the monolayer resist and the silicon-containing intermediatelayer, which allows for thickness reduction of the monolayer resist. Themethod for forming the undercoat layer in this case includes a coatingand baking method and a CVD method. In the case of coating, novolacresins and resins obtained by polymerization of fused ring-containingolefins are used. In the CVD film formation, gases such as butane,ethane, propane, ethylene and acetylene are used. For thesilicon-containing intermediate layer, either a coating method or a CVDmethod may be employed. The coating method uses silsesquioxane, cageoligo-silsesquioxane (POSS) and the like while the CVD method usessilane gases as the reactant. The silicon-containing intermediate layermay have an antireflection function with a light absorbing ability andhave photo-absorptive groups like phenyl groups, or it may be a SiONfilm. An organic film may be formed between the silicon-containingintermediate layer and the photoresist, and the organic film in thiscase may be an organic antireflective coating. After the photoresistfilm is formed, deionized water rinsing (or post-soaking) may be carriedout for extracting the acid generator and the like from the film surfaceor washing away particles, or a protective film may be coated.

With a mask having a desired pattern placed above the resist film, theresist film is then exposed to actinic radiation such as UV, deep-UV,electron beams, x-rays, excimer laser light, y-rays and synchrotronradiation. The exposure dose is preferably about 1 to 200 mJ/cm², morepreferably about 10 to 100 mJ/cm². The film is further baked on a hotplate at 60 to 150° C. for 1 to 5 minutes, preferably 80 to 120° C. for1 to 3 minutes (post-exposure baking=PEB). Thereafter the resist film isdeveloped with a developer in the form of an aqueous base solution, forexample, 0.1 to 5 wt %, preferably 2 to 3 wt % aqueous solution oftetramethylammonium hydroxide (TMAH) for 0.1 to 3 minutes, preferably0.5 to 2 minutes by conventional techniques such as dip, puddle or spraytechniques. In this way, a desired resist pattern is formed on thesubstrate. It is appreciated that the resist composition of theinvention is suited for micro-patterning using such high-energyradiation as deep UV with a wavelength of 254 to 193 nm, vacuum UV witha wavelength of 157 nm, electron beams, soft x-rays, x-rays, excimerlaser light, γ-rays and synchrotron radiation, and best suited formicro-patterning using high-energy radiation in the wavelength range of180 to 200 nm.

Immersion lithography can be applied to the resist composition of theinvention. The ArF immersion lithography uses a liquid having arefractive index of at least 1 and least absorptive to exposureradiation, such as deionized water or alkanes as the immersion solvent.The immersion lithography involves prebaking a resist film and exposingthe resist film to light through a projection lens, with deionized wateror similar liquid interposed between the resist film and the projectionlens. Since this allows projection lenses to be designed to a numericalaperture (NA) of 1.0 or higher, formation of finer patterns is possible.The immersion lithography is important for the ArF lithography tosurvive to the 45-nm node, with a further development thereof beingaccelerated. In the case of immersion lithography, deionized waterrinsing (or post-soaking) may be carried out after exposure for removingwater droplets left on the resist film, or a protective coating may beapplied onto the resist film after pre-baking. for preventing anydissolution from the resist and improving water slip on the filmsurface. The resist protective coating used in the immersion lithographyis preferably formed from a solution of a polymer having1,1,1,3,3,3-hexafluoro-2-propanol residue which is insoluble in water,but dissolvable in an alkaline developer liquid, in a solvent selectedfrom alcohols of at least 4 carbon atoms, ethers of 8 to 12 carbonatoms, and mixtures thereof.

The technique enabling the ArF lithography to survive to the 32-nm nodeis a double patterning process. The double patterning process includes atrench process of processing an underlay to a 1:3 trench pattern by afirst step of exposure and etching, shifting the position, and forming a1:3 trench pattern by a second step of exposure for forming a 1:1pattern; and a line process of processing a first underlay to a 1:3isolated left pattern by a first step of exposure and etching, shiftingthe position, processing a second underlay formed below the firstunderlay by a second step of exposure through the 1:3 isolated leftpattern, for forming a half-pitch 1:1 pattern.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. Mw is weight average molecular weight.

EXAMPLES AND COMPARATIVE EXAMPLES [Preparation of Resist Material]

Resist solutions were prepared by dissolving a polymer, acid generator,and basic compound in a solvent in accordance with the formulation shownin Table 1 and passing through a Teflon® filter with a pore size of 0.2μm. In all runs, the solvent contained 0.01 wt % of surfactant KH-20(Asahi Glass Co., Ltd.).

TABLE 1 Resist Resin Acid generator Base Solvent 1 Solvent 2 R-01P-01(80) PAG-1(6.5) Base-1(1.2) PGMEA(780) CyHO(340) R-02 P-02(80)PAG-1(6.5) Base-1(1.2) PGMEA(780) CyHO(340) R-03 P-03(80) PAG-1(6.5)Base-1(1.2) PGMEA(780) CyHO(340) R-04 P-04(80) PAG-1(6.5) Base-1(1.2)PGMEA(780) CyHO(340) R-05 P-05(80) PAG-1(6.5) Base-1(1.2) PGMEA(780)CyHO(340) R-06 P-06(80) PAG-1(6.5) Base-1(1.2) PGMEA(780) CyHO(340) R-07P-07(80) PAG-1(6.5) Base-1(1.2) PGMEA(780) CyHO(340) R-08 P-08(80)PAG-1(6.5) Base-1(1.2) PGMEA(780) CyHO(340) R-09 P-09(80) PAG-1(6.5)Base-1(1.2) PGMEA(780) CyHO(340) R-10 P-10(80) PAG-1(6.5) Base-1(1.2)PGMEA(780) CyHO(340) R-11 P-11(80) PAG-1(6.5) Base-1(1.2) PGMEA(780)CyHO(340) R-12 P-12(80) PAG-1(6.5) Base-1(1.2) PGMEA(780) CyHO(340) R-13P-03(80) PAG-1(5.0) Base-1(0.9) PGMEA(780) CyHO(340) R-14 P-03(80)PAG-1(6.0) Base-1(1.1) PGMEA(780) CyHO(340) R-15 P-03(80) PAG-1(7.0)Base-1(1.3) PGMEA(780) CyHO(340) R-16 P-03(80) PAG-2(6.5) Base-1(1.2)PGMEA(780) CyHO(340) R-17 P-03(80) PAG-1(6.5) Base-2(1.2) PGMEA(780)CyHO(340) R-18 P-03(80) PAG-1(3.25) Base-1(1.2) PGMEA(780) CyHO(340)PAG-2(3.25) The values in parentheses are in parts by weight.

Resist solutions for comparison were similarly prepared using theformulation shown in Table 2.

TABLE 2 Resist Resin Acid generator Base Solvent 1 Solvent 2 R-19P-13(80) PAG-1(6.5) Base-1(1.2) PGMEA(780) CyHO(340) R-20 P-14(80)PAG-1(6.5) Base-1(1.2) PGMEA(780) CyHO(340) The values in parenthesesare in parts by weight.

In Tables 1 and 2, the acid generator, base and solvent are designatedby abbreviations, which have the following meaning.

-   PAG-1: triphenylsulfonium    1,1,3,3,3-pentafluoro-2-tert-butylcarbonyloxypropanesulfonate-   PAG-2: triphenylsulfonium nonafluorobutanesulfonate-   Base-1: N-{2-(2-methoxyethoxymethoxy)ethyl}morpholine-   Base-2: N-(2-acetoxyethyl)benzimidazole-   PGMEA: 1-methoxyisopropyl acetate-   CyHO: cyclohexanone

The resins designated by abbreviations in Tables 1 and 2 are polymersconstructed as in Tables 3 to 7.

TABLE 3 Resin Unit 1 Unit 2 Unit 3 Unit 4 Mw P-01 A-1M(0.25) B-1M(0.40)C-1M(0.25) D-1M(0.10) 7,100 P-02 A-1M(0.20) B-1M(0.40) C-1M(0.25)D-1M(0.20) 7,300 P-03 A-1M(0.25) B-1M(0.40) C-1M(0.25) D-2M(0.10) 6,500P-04 A-1M(0.25) B-1M(0.40) C-1M(0.25) D-3M(0.10) 7,800 P-05 A-1M(0.25)B-1M(0.40) C-1M(0.25) D-4M(0.10) 7,500 P-06 A-1M(0.30) B-1M(0.25)C-1M(0.25) D-1M(0.20) 6,800 P-07 A-1M(0.35) B-1M(0.20) C-1M(0.25)D-1M(0.20) 7,300 P-08 A-1M(0.30) B-1M(0.25) C-1M(0.25) D-1M(0.20) 7,000P-09 A-1M(0.30) B-2M(0.25) C-1M(0.25) D-1M(0.20) 6,900 P-10 A-1A(0.30)B-1M(0.25) C-1M(0.25) D-1M(0.20) 6,400 P-11 A-1M(0.30) B-1M(0.25)C-2M(0.25) D-1M(0.20) 6,500 P-12 A-1A(0.30) B-1A(0.25) C-1A(0.25)D-1A(0.20) 6,700 P-13 A-2M(0.25) B-1M(0.40) C-1M(0.25) D-3M(0.10) 6,800P-14 A-3M(0.25) B-1M(0.40) C-1M(0.25) D-3M(0.10) 7,500 The value inparentheses is an incorporation ratio of a particular unit expressed inmolar ratio.

TABLE 4 A-1M (R = CH₃) A-2M (R = CH₃) A-3M (R = CH₃) A-1A (R = H) A-2A(R = H) A-3A (R = H)

TABLE 5 B-1M (R = CH₃) B-2M (R = CH₃) B-1A (R = H) B-2A (R = H)

TABLE 6 C-1M (R = CH₃) C-2M (R = CH₃) C-1A (R = H) C-2A (R = H)

TABLE 7 D-1M (R = CH₃) D-2M (R = CH₃) D-1A (R = H) D-2A (R = H)

D-3M (R = CH₃) D-4M (R = CH₃) D-3A (R = H) D-4A (R = H)

Resolution Test

On silicon wafers having an antireflective coating (ARC29A, NissanChemical Industries Ltd.) of 78 nm thick, the resist solutions (R-01 to18) of the invention and comparative resist solutions (R-19 and 20) werespin coated, then baked at 110° C. for 60 seconds to give resist filmshaving a thickness of 160 nm. Using an ArF excimer laser stepper (NikonCorp., NA 0.85), the resist films were exposed, baked (PEB) for 60seconds and then puddle developed for 60 seconds with a 2.38 wt %aqueous solution of tetramethylammonium hydroxide. In this way, 1:1line-and-space patterns were formed. The PEB step used an optimumtemperature for a particular resist composition.

The pattern-bearing wafers were observed under a top-down scanningelectron microscope (TDSEM). The optimum exposure was an exposure dose(mJ/cm²) which was irradiated through a mask with a feature size of 65nm to provide an on-wafer size of 65 nm to a 1:1 line-and-space pattern.The range of focus within which a 1:10 isolated line pattern from a maskfeature size of 180 nm was formed at the optimum exposure was determinedand reported as a focal depth (a wider range is better). The 65-nmline-and-space pattern was observed for roughness, and line edgeroughness (LER) was evaluated in three ratings of Good, Fair, and Poor.

Tables 8 and 9 tabulate the test results (focal depth, pattern profile,and LER) of the inventive and comparative resist compositions,respectively.

TABLE 8 Exam- PEB Optimum Focal Pattern ple Resist temp. exposure depthprofile LER 01 R-01 105° C. 42.0 mJ/cm² 0.10 μm Rectangular Good 02 R-02110° C. 43.0 mJ/cm² 0.10 μm Rectangular Good 03 R-03 110° C. 41.0 mJ/cm²0.10 μm Rectangular Good 04 R-04 110° C. 41.0 mJ/cm² 0.10 μm RectangularFair 05 R-05 110° C. 41.0 mJ/cm² 0.10 μm Rectangular Fair 06 R-06 105°C. 40.0 mJ/cm² 0.10 μm Rectangular Fair 07 R-07 100° C. 44.0 mJ/cm² 0.05μm Somewhat Good rounded top 08 R-08 105° C. 42.0 mJ/cm² 0.10 μmRectangular Good 09 R-09 105° C. 42.0 mJ/cm² 0.10 μm Rectangular Fair 10R-10 105° C. 40.0 mJ/cm² 0.10 μm Rectangular Fair 11 R-11 105° C. 41.0mJ/cm² 0.10 μm Rectangular Good 12 R-12 105° C. 42.0 mJ/cm² 0.10 μmRectangular Good 13 R-13 110° C. 40.0 mJ/cm² 0.10 μm Rectangular Good 14R-14 105° C. 40.0 mJ/cm² 0.10 μm Rectangular Fair 15 R-15 100° C. 42.0mJ/cm² 0.10 μm Rectangular Good 16 R-16 105° C. 41.0 mJ/cm² 0.10 μmRectangular Good 17 R-17 105° C. 43.0 mJ/cm² 0.05 μm Somewhat Fairrounded top 18 R-18 105° C. 44.0 mJ/cm² 0.10 μm Rectangular Good

TABLE 9 Com- parative Exam- PEB Optimum Focal Pattern ple Resist temp.exposure depth profile LER 01 R-19 105° C. 43.0 mJ/cm² 0.05 μm Roundedtop Poor 02 R-20 115° C. 41.0 mJ/cm² 0.10 μm Rounded top Poor

It is seen from the results of Table 8 that the resist compositionswithin the scope of the invention (Examples 1 to 18) have a wide focaldepth and form patterns with improved LER. Table 9 reveals thatComparative Examples 1 and 2 which use only customary tertiary esterprotective groups for carboxylic acid protection are inferior in patternprofile and LER to the inventive resist compositions. It has beendemonstrated that a resist composition which uses a polymer comprisingspecific recurring units as a base resin according to the invention isimproved in resist performance, as compared with resist compositions ofthe prior art design.

Japanese Patent Application No. 2006-321870 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A positive resist composition comprising (A) a resin component whichbecomes soluble in an alkaline developer under the action of an acid and(B) a compound capable of generating an acid in response to actiniclight or radiation, wherein said resin component (A) is a polymercomprising recurring units having the general formula (1):

wherein R¹ is each independently hydrogen, methyl or trifluoromethyl, R²is hydrogen or CO₂R⁴, R³ is a fluorinated substituent group of 1 to 15carbon atoms, R⁴ is a straight, branched or cyclic monovalenthydrocarbon group of 1 to 20 carbon atoms which may contain aheteroatom, m is 1 or 2, n is 1 or 2, a, b, c, and d indicative ofratios of the corresponding recurring units each are a number from morethan 0 to less than 1, and a+b+c+d=1.
 2. A process for forming apattern, comprising the steps of applying the positive resistcomposition of claim 1 onto a substrate to form a resist coating, heattreating the resist coating and exposing it to high-energy radiation orelectron beam through a photomask, and heat treating the exposed coatingand developing it with a developer.
 3. A process for forming a patternaccording to claim 2, wherein the exposing step is effected by theimmersion lithography wherein a liquid having a refractive index of atleast 1 intervenes between the resist coating and a projection lens. 4.A process for forming a pattern according to claim 3, wherein saidprocess further comprises the step of applying a protective coating onthe resist coating, and the exposing step is effected by the immersionlithography wherein a liquid having a refractive index of at least 1intervenes between the protective coating and a projection lens.